In a wireless communication system in which transmission from a plurality of base stations is performed at the same time and the same frequency, transmission frequencies of all the base stations are the same. In practice, however, frequency errors of oscillators of the respective base stations are different from each other, and thus the transmission frequency of each of the base stations is a frequency having a respectively different offset (an error) from an ideal frequency. Therefore, a reception signal of a mobile station is a signal in which a plurality of signals having different frequency offsets are superposed. In the mobile station, it is difficult to perform frequency offset compensation on a combined wave serving as a reception wave in which a plurality of signals having different frequency offsets are superposed on each other, and thus the reception characteristics of the mobile station are degraded.
Patent Literature 1 discloses an invention of cancelling the frequency offset described above. In a mobile communication system described in Patent Literature 1, a base station detects a frequency offset from a reception signal from a mobile station and performs complex multiplication of a phase opposite to a phase of the detected frequency offset with a transmission signal in a time domain, that is, performs phase rotation on a transmission signal, thereby executing frequency control of the transmission signal. In this way, a frequency offset between each base station and a mobile station can be cancelled, and thus when transmission is performed from a plurality of base stations to a mobile station at the same frequency, a reception wave of the mobile station is a combined wave in which signals having a frequency offset of 0 are superposed on each other, and it is possible to suppress degradation in the reception characteristics of the mobile station.